Deioned water

used as working fluid

flowed through the quartz glass microtubes with inner diameters of 45 μm

92 μm and 141 μm

respectively

and the influence of viscous dissipation on convective heat transfer was experimentally studied.The microtube was heated by an electrified brass wire that was coiled evenly up around the microtube.As the Reynolds number varied in the range from 100 to 2000 in the experiments the corresponding Nusselt number was obtained.The quantity of heat generated by viscous dissipation was calculated by considering electrical double layer (EDL) effect.The experimental results showed that the influence of viscous dissipation on convective heat transfer was small at a low Reynolds number.With the increase of Reynolds number and the decrease of microtube inner diameter

viscous dissipation apparently affected convective heat transfer.For the microtube with an inner diameter of 45 μm

the quantity of heat generated by the viscous dissipation could account for about 14.1% of the quantity of convective heat transfer when Reynolds number reached 2000.The influence of viscous dissipation on convective heat transfer was so small that it could be neglected for microtube with an inner diameter of 141 μm when the flow was laminar.